1. Field of the Invention
The present invention relates to a strip-like brush seal having a plurality of thin plates each of which is processed to have thin, cantilever beams at its one end and to a brush seal device, for sealing between a rotational shaft and a mating component movable relatively, for example in an aircraft and a gas turbine.
More particularly, the present invention relates to a technical field of a brush seal having thin beams that are protected from having scratches or damages.
2. Description of the Related Art
As shown in FIG. 8, there exists a brush seal device 100 as a prior art of the present invention.
FIG. 8 is a sectional view of a brush seal device 100 mounted between a rotational shaft 120 and a casing 110 through which the rotational shaft 120 passes. The casing 110 is a component of a steam turbine or gas turbine. The brush seal device 100 seals fluid by separating the casing 110 and the rotational shaft 120.
In FIG. 8, the brush seal device 100 is formed in a ring shape and attached to a channel section 112 of the casing 110. Main components of the brush seal device 100 are a brush seal 109, a back plate 102 and a retaining plate 103. In the brush seal 109, a number of bristles 101 are formed into a bundle, which is in turn arranged circumferentially in the form of a wall. The bristles 101 are welded together at their outer ends to form an attachment section 104. The free end face 105 as the other end of the brush seal 109 faces the rotational shaft 120.
The diameter of each bristle 101 used in general is 0.02 to 0.5 mm. However, its sealing ability is poor because the bristle 101 is linear. In order to overcome such a drawback the thickness of the bundle of bristles 101 must be increased and thus tens of thousands or hundreds of thousands of bristles are necessarily used.
For such a brush seal 109 as described, countless number of these bristles 101 must be cut to has uniform length and then aligned circumferentially. it is therefore difficult to align them precisely. Further, it is also difficult to assemble with uniform accuracy in mass production. This causes defects.
An annular back plate 102 is disposed on one side face of the brush seal 109 with its side face 108 contacting the one side face of the brush seal 109 and bears the bristles 101 against the action of the sealed fluid pressure. A retaining plate 103 formed as a ring plate is disposed integrally on the other side face of the brush seal 109 to sandwich, in cooperation with the back plate 102, the brush seal 109 on its attachment section 104 side. The retaining ring 103 has a small thickness in its radial direction so that the brush seal 109 is exposed to allow to deform itself, corresponding to the contact of the rotational shaft 120 therewith.
The back plate 102, the attachment section 104 of the brush seal 109 and the retaining plate 103 are welded, with the attachment section 104 being located between the others, to form a connecting section 106. The welded components are thermally deformed due to different materials among them and then some rework will be required, resulting in the increase of processing cost.
FIG. 9 is a partial front view, showing a state that the brush seal 109 fits normally without oscillation of the rotational shaft 120, as shown by an actual line in FIG. 8. The bristles 101 fit and extend straight, while incline in the rotating direction with respect to the radial direction of the rotational shaft 120. Accordingly, after completion as a brush seal 109, the fitting surface of the free end 105 is precisely finished so as to fit the rotational shaft 120 normally, as shown FIG. 11, which is a perspective view of the brush seal 109, seen from the inner circumferential side thereof.
It is also difficult to process the free end 105 because the number of bristles in the form of a bundle is extremely large, such as several ten thousands and they are apt to deform. Furthermore, when the brush seal 109 having a finished free end 105 is, for example mounted, each bristle is deformed easily if it contacts or strikes any other parts. Such deformation will adversely affect on the sealing ability.
When the rotational shaft 120 contacts the free end 105 of the brush seal 109 as shown in FIG. 10, the brush seal 109 is pressed against the rotational shaft 120, while its tilt angle is increased. During this state, the contact of the brush seal 109 with the rotational shaft 120 will be facilitated if there is some defective deformation at the free end 105 of each bristle 101, resulting in its rapid wear.
In this state, as shown in FIG. 8, if the pressure of the sealed fluid is a high pressure P1, the differential pressure (P1-P2) between P1 and a low pressure P2 is increased and the sealing ability is worsened due to the deformation and wear on the free end 105.
In the brush seal 2 constituted as described, each bristle 101 is a thin wire and its free end 105 is therefore apt to deform. During fabrication of the brush seal 2, the free end 105 of the bristle may be deformed. Further, if it were not deformed during fabrication then the free end 105 might be bent when the brush seal 2 is installed on the casing 130.
Also, it is difficult to finish exactly the end face of the free end 105 of the brush seal 2 so as to fit the rotational shaft 120, resulting in the increase of processing cost.
Additionally, it is also difficult to weld the attachment section while the inner diameter formed by the end face of the free end 105 is made uniform. Because several ten thousands of bristles 101 are required to constitute a brush seal.
The present invention has been made in consideration of the problems as mentioned above, and technical problems of the invention are to allow to fabricate a brush seal unit without damages on the brush section of the brush seal and also allow to pile the brush seal units without damages and bent thereon.
Further technical problems of the present invention are to allow to provide a thin elastic wire capable of elastically deforming, corresponding to the contact of the brush seal with the rotational shaft and also allow to assemble the brush seal unit without damages on the brush section, even if thin wires are employed. Further yet technical problems are to improve the yield of material for fabricating the brush seals and to increase processing accuracy thereof.
Still other technical problems are to provide a brush seal with good ability of the brush seal to follow in response to the relative displacement between the brush seal and the outer circumference of the rotational shaft for improving the sealing ability and to improve the sealing ability of the contact or proximity between the brush seal and the rotational shaft.
The present invention has been made to solve the problems as mentioned above, and technical means for solving the problems are constituted as below.
A brush seal of first preferred embodiment according to the present invention is a brush seal mounted on one of two components that are relatively rotated, for sealing the clearance given between the two components, comprising: a plurality of the brush seal units, each having a strip-like brush section on the side facing the other component and having a base plate section on the side opposing the brush section side, the brush section being formed with thin beams each of which is between two slits, and the base plate section being fixed to the one component; the brush seal unit having, at the free end of the brush section, an ablative plate section integrally formed therewith and having a thin groove at the boundary between the brush section and the ablative plate section; wherein the ablative plate section is broken off at the groove before mounting the brush seal to be placed between the two components.
In the brush seal of the present invention, an ablative plate section is formed together with the free end of the brush section in the brush seal unit, thereby to allow to protect the brush section. In other words, a number of thin beams are prevented from bending if the brush section strikes and contacts other members.
Furthermore, a groove is formed at the root of the ablative plate section such that the thickness of its bottom wall is processed to be thin with half-etching process. Accordingly, the brush seal unit or the brush seal can be obtained by bending to break off the ablative plate section when the brush seal units are piled, or when the brush seal is installed on the rotor as a component.
Additionally, it is allowed to improve processing accuracy in the fabrication of the brush seals because they are made from a thin plate and also allowed to mount the brush seal extremely easily.